1. Field of the Invention
The invention relates to a fitting for thick-walled pipes, having a contact region and a pressing region, the pressing region being arranged on the side of the contact region facing towards the pipe insertion opening. The invention also relates to a system consisting of a pipe and a fitting, and to the use of the fitting to connect thick-walled pipes. The invention furthermore relates to a method for producing a fitting for thick-walled pipes, in which a thick-walled pipe is radially widened in a fitting region arranged at one pipe end so that the internal diameter of the fitting region corresponds substantially to the external diameter of the pipe and the wall thickness in the fitting region corresponds substantially to the wall thickness of the rest of the pipe, and in which a subregion of the fitting region, arranged at the pipe end, is radially stretched so that the internal diameter of the subregion is greater than the external diameter of the pipe.
2. Description of Related Art
In order to transport fluid media, for example, water, over large distances, pipes or pipe systems made of inexpensive alloys are often used in the prior art to save cost. These alloys are often not corrosion-resistant, so that the pipes gradually corrode superficially on their inside owing to the mediums conveyed in them. Typical material erosion for such surface corrosion lies in the range of from 100 to 150 μm per year.
In order to ensure a sufficient lifetime of the pipes despite the corrosion, thick-walled pipes are predominantly used so that the pipe remains leaktight for typical periods of from 10 to 30 years despite the annual material erosion. Thus, according to DIN EN 10255, medium-weight pipes with a nominal thickness of ½″ have a wall thickness of 2.6 mm and pipes with a nominal width of 4″ have a wall thickness of 4.5 mm. In terms of the surface corrosion, it is particularly important for the pipe walls in contact with the medium to have a uniform thickness, since locally thinner-walled points would otherwise lead to premature rusting through and, therefore, to leakage. The lifetime of such pipe systems is thus dependent on the wall thickness of the thinnest-walled point in contact with the medium.
The fittings used to connect the pipes represent a particular weak point. They usually likewise consist of a material which is not corrosion-resistant and, therefore, if rusting through is intended to be prevented, they must also have large wall thicknesses like the pipes.
For the production of a leaktight connection between a fitting and a pipe, in the case of thin-walled pipes with nominal widths of between 15 and 108 mm, it is conventional to compress the fitting with the thin-walled pipe. It has been found that long-term leaktightness of the connection is ensured in this way. Such a connection is disadvantageous for thick-walled pipes since, owing to the large wall thickness of the fittings used to connect thick-walled pipes in the prior art, such compression is very difficult because of the high rigidity of the thick-walled fittings and is possible only with very high force application using particularly elaborate and expensive pressing tools. For this reason, in the prior art such a fitting is conventionally not connected to a thick-walled pipe by compression, but in a different way. In particular, threaded connectors according to DIN EN 10242 based on screws and clamps are used. The installation of such connections is time consuming and is accompanied by a laborious preparation of the pipe ends to be connected. Such connections, further more, have the disadvantage that they do not achieve the durability of compressed connections and/or they require more elaborate and, therefore, more expensive fittings.